The present invention relates to a quick coupler for an excavator, and more particularly to such a quick coupler, which is provided on each lower end side of an excavator arm and a link in the excavator in such a manner that it facilitates mounting or detaching of an accessory to be exchanged depending on work conditions, such as a bucket, a breaker, a crusher, a vibration hammer or the like.
In general, an excavator is an equipment which performs a variety of constructional works, for example, excavating the ground, removing soil or sand, crushing rocks, breaking pavements paved with asphalt or concrete and so forth by a selected accessory (a bucket, a breaker, a crusher, a vibration hammer, etc.) corresponding to work conditions.
Now, an excavator with a bucket mounted thereon will be described in detail for the purpose of illustrating a conventional quick coupler for an excavator.
FIG. 1 is a perspective view of an excavator with a conventional coupler attached thereto, and FIG. 2 is a sectional view of the conventional quick coupler for use in the excavator. Since the quick coupler is bilaterally symmetrical, the following description will be given only for one symmetrical side of the quick coupler.
As shown FIGS. 1 and 2, the excavator has a structure in which a first link 41 cooperates with a second link 42 to drive the bucket 4 in accordance with forward and backward movements of a working cylinder 40.
In such an excavator, the conventional quick coupler for coupling an excavator arm 1 with the bucket 4 is provided between lower ends of the excavator arm 1 and the second link 42, and, as shown in FIG. 2, is so constructed that a piston 30 is expanded and inserted into a pinhole 25a of the bucket 4 to couple the excavator arm 1 with the bucket 4 when hydraulic pressure is supplied to an advance pressure chamber 32 through an advance port 28.
In the conventional coupler, however, a piston seal 34 is disposed on an outer circumferential surface of the piston 30, which causes a problem that external contaminants are introduced into an astem pressure chamber 32a to adulterate hydraulic working oil therein and thus to shorten the life span of the overall hydraulic system when the piston 30 is dented or abraded. Also, if a load is imposed on any one side piston 30 due to its dent or abrasion, the other side piston 30 bearing no load is moved toward the one with the load imposed, thereby causing the astern pressure chamber 32a to be opened outward. Besides, when the piston 30 is directly inserted into the pinhole 25a, it may be deformed or damaged due to a fact that it is subjected to a perpendicular axial external force (radial force) between the excavator arm 1 and the bucket 4.
That is, since the piston 30 is not allowed to be flexible in structure, it is easily deformed (for example, bent) or damaged on its surface. As the result, oil leakage may occur, the piston 30 may be not operate well and lose its function. Ultimately, the piston 30 must be replaced early.
The conventional quick coupler has also a problem in that it is difficult to position the pinhole 25a and the piston 30 in a centered position when the quick coupler is joined with the bucket 4.
Accordingly, the present invention has been made to overcome the above-mentioned problems, and it is an object of the present invention to provide a quick coupler for an excavator, which is mounted on each lower end side of an excavator arm and a link of the excavator in such a manner that it facilitates mounting or detaching of an accessory, such as a bucket, a breaker, a crusher, a vibration hammer or the like to be exchanged depending on work conditions.
It is another object of the present invention to provide a quick coupler for an excavator, which is bilaterally symmetrical and always constant in its forward and backward movement lengths without distorting joints of the excavator, and prevents contaminants from being mixed into hydraulic working oil by a triple sealing structure of a mechanical seal, a cover seal and a rod seal.
It is still another object of the present invention to provide a quick coupler for an excavator, which easily and simply allows centering between a joining pinhole of the accessory and a coupler pin by attaching a position guide, and in which the coupler pin having flexibility has no effect on a working piston even when it is subjected to a perpendicular axial external force (radial force).
To accomplish these objects, there is provided a quick coupler for an excavator in accordance with the present invention, the quick coupler comprising: a cylinder tube fixed to each lower end of an excavator arm and a link, and having fixing bolt holes formed on one side thereof; a piston housing fitted into the cylinder tube to be fixed by fixing bolts inserted into the fixing bolt holes, and joined with a rod cover at both ends thereof, respectively; a pair of pistons inserted into each side of the piston housing with a spring interposed therebetween, each piston having a mechanical seal formed at its inner end; the pair of rod covers inserted between an outer circumference of the piston and an inner circumference of the piston housing on each side of the piston housing for preventing leakage of hydraulic fluid; and a pair of coupler pins inserted between an outer circumference of the piston housing and an inner circumference of the cylinder tube on each side of the cylinder tube, each coupler pin formed in a cap-shape.
Preferably, one end of the coupler pin is formed with a predetermined number of axial tightening bolt holes which penetrate a part of a ring groove formed on the coupler pin side, and an inner diameter of a conjugation groove formed on an inner side of the coupler pin is larger than an outer diameter of the piston.
It is also preferred that a cover seal for preventing oil leakage is provided in a contact portion between the rod cover and the piston housing, and a rod seal for preventing oil leakage is similarly provided in a contact portion between the rod cover and the piston.
A pin seal for preventing inflow of contaminants is further provided in an inlet portion of the cylinder tube with which the coupler pin is brought into sliding contact.
Moreover, an advance port is mounted to penetrate the cylinder tube and the piston housing in one position to supply hydraulic pressure to an advance pressure chamber; the piston housing is formed with a longitudinal pressure line that leads into an astern pressure chamber, and an astern port is mounted to penetrate the cylinder tube and the piston housing in another position and connected with the pressure line to supply hydraulic pressure to the astern pressure chamber.
Furthermore, position guides in a semicircular-shape are preferably attached to upper portions of both ends of the excavator arm and a lower end of the link, respectively to allow centering between the joining pinhole and the coupler pin.